EXSC 223 9th EditionExam # 3 Study Guide Lectures: 1 - 10Lecture 1 (March 17)Muscle Twitch1) Latent period – the period after stimulation, but before muscle tension is generateda. Is the same length for fast and slow twitch muscles2) Contraction period – cross-bridges are formed repeatedly; cross-bridge cycling3) Relaxation period – Calcium is decreased in muscle cells by being pumped from cytosolA muscle twitch is the result of a single stimulus, causing on action potential.Fast twitch – develops tension quickly and relaxes quicklySlow twitch – tensioin develops slowly and relaxes slowlyHow do we control muscle tension?1)Frequency of stimulation – based on muscle twitcha. Summation – more tension is developed when a muscle is stimulated again before it relaxesb. Fused tetanus – the maximum number of cross-bridges that a muscle can form.c. The amount of tension a muscle develops depends on the number of cross-bridges formed.d. The more calcium is in the muscle, the more cross-bridges can be formed.2)Motor unit recruitmenta. Motor unit – a motor neuron and all the muscle fibers that it innervatesb. The more motor units are used, the greater the muscle tension.c. This is a more precise way of controlling muscle tension.Size Principle – a greater contraction force is produced by a greater number of motor units contractingLecture 2 (March 19)Length-Tension Relationship – the maximum tension of a muscle is produced in its optimal length, between 80% and 120% of resting length.- Tension decreases when a muscle is stretched beyond optimal length because there is lessoverlap of thick and thin filaments.- When a muscle is shortened beneath optimal length, the thin filaments overlap too much, thus preventing cross-bridge formation.Smooth MuscleA) Developmenti. Not a uniform phenotypeii. Single, central nucleusiii. Synchronous contraction made possible by multiple cellular junctionsiv. No striationsB) Neural Controli. Autonomic nervous system – parasympathetic/sympatheticii. No neuromuscular junction/motor neuron involved in contractionC) Type of Contractioni. Phasic contraction – single unitii. Tonic contraction – multi unitNeural ControlInstead of having neuromuscular junctions like skeletal muscle, smooth muscle has varicosities that release the neurotransmitter Ach into diffuse junctionsVaricosity – a bulbous swelling of innervating nervesFunctional Structures- Intermediate filaments- Caveolae- Thick and thin filaments (without troponin)- Ratio of thin to thick filaments is 1:13E-C CouplingCa2+ binds to calmodulin, causing it to change shape. This activates kinase, which attaches a phosphate group to myosin. This induces the power stroke (contraction).*Be able to compare/contrast EC coupling in smooth muscle with EC coupling in skeletal muscleTypes of Smooth Muscle1) Single Unit – visceral musclea. Contract rhythmically as a unitb. Electrically coupled via gap junctionsc. May exhibit spontaneous action potentialsd. Arranged in opposing sheets and exhibit stresse. Found in stomach, esophagus, intestinesPeristalsis – alternating contractions and relaxations of smooth muscles that mix and squeeze substances through the lumen of hollow organs- When longitudinal layer contracts the organ dilates and shortens- When circular layer contracts the organ elongates2) Multi-unita. Rare gap junctionsb. Infrequent spontaneous depolarizationsc. Structurally independent muscle fibersd. Rich nerve supply, may form motor unitse. Graded contractionsf. Found in large airways to lungs, large arteries, erector pili, and internal eyeResponse to StressStress-relaxation response – smooth muscle responds to stress only briefly, and then adapts to its new lengthEx: Stomach stretches when you eat a lot.Lecture 3 (March 21)Chapter 24Metabolism – A series of biochemical reactions inside cells involving substances being built and broken down.1) Anabolism – synthesizing large molecules from small onesi. Amino acids bond to form proteinsii. Glucose molecules bond to form glycogen2) Catabolism – hydrolysis of complex structures to simpler onesi. Proteins break down into amino acidsii. Glucose is hydrolyzed into H2O and CO2Cellular Respiration – Catabolism of food to form ATP in cells.C6H12O6 + O6 → CO2 + H2O is catabolic and ADP + Pi → ATP is anabolicATP is used to drive reactions (cross-bridge cycling) and regulate enzymes (phosphorylation).3 Stages of Metabolism:1) Digestion, absorption, and transport2) Anabolism and catabolism of nutrients3) Oxidative breakdown in mitochondria forming water; some energy released is used to make ATPOxidation-Reduction ReactionsOxidation – gain of oxygen or loss of hydrogen (electrons are lost with hydrogen)-Energy is lostReduction – gain of hydrogen (and electrons) or loss of oxygen-Energy is gainedRedox reactions are catalyzed by enzymes- Dehydrogenases – remove H atoms- Oxidases – transfer oxygen atomsMost enzymes require help from coenzymes, which are usually derived from B vitamins. Coenzymes (NAD+ and FAD) act as hydrogen (electron) acceptors.ATP Synthesis1) Substrate-level phosphorylation – high-energy phosphate groups are transferred directlyfrom phosphorylated substrates to ADPi. ADP + Pi + substrate → ATP + productii. This happens once in glycolysis and once per Krebs cycle2) Oxidative phosphorylationi. More complex; produces most of a cell’s ATPChemiosmotic process – potential energy created by more H+ atoms outside the inner mitochondrial membrane (hydrogen gradient).Lecture 4 (March 24)Carbohydrate Metabolism1) Anaerobic breakdown of glucosea. Glycolysis: C6H12O6 → 2C3H6O3 (pyruvate)+ 2ATP + heat2) Aerobic oxidation of glucosea. C6H12O6 +6O2 → 6H2O + 6CO2 + 32ATP + heatb. Complete glucose catabolism requires 3 pathways: glycolysis, krebs cycle, and oxidative phosphorylationGlycolysis- 10-step pathway that occurs in cytosol- An anaerobic process, meaning it does not use oxygen and occurs whether or not oxygen is present- Produces 2 pyruvate molecules- 3 major phases: sugar activation (investment), cleavage, and oxidation & ATP formation1) Sugar Activation – Glucose phosphorylated twice, using 1 ATP molecule each time2) Cleavage – Phosphorylated glucose molecule is split into two 3-carbon fragments that are not identical, but are isomers.3) Oxidation and ATP Formation – Two 3-carbon fragments are oxidized and NAD+ picks up removed H+. Phosphate groups are